1. Field
Embodiments described herein generally relate to methods of forming hardmask materials for semiconductor devices. More specifically, embodiments described herein relate to the development of a high etch selective hardmask material by ion implantation into amorphous carbon films.
2. Description of the Related Art
Hardmasks are used to fabricate NAND and dynamic random access memory (DRAM) devices. Hardmasks are commonly used as sacrificial layers in lithographic patterning and enable, through an etching process, the patterning of features onto a layer of a semiconductor device. The patterned features can form, for example, the transistors and interconnects that allow the NAND and DRAM devices to operate.
The important properties of a hardmask material are etch resistance, compressive stress, mechanical properties, and removability. An ideal hardmask has a high etch resistance compared to the layer to be etch (hereinafter, an “underlayer”) so that the underlayer etches in an etch process whereas the hardmask does not. A high etch resistance allows efficient transfer of the pattern of the hard mask to the underlayer. Etch resistance generally shows a positive correlation with hardmask density. An ideal hardmask also has a low compressive stress. A lower compressive stress eliminates undesirable wafer bow after hardmask deposition, which can make further device fabrication difficult. In addition, an ideal hardmask has strong mechanical properties. For example, a high modulus (Young's modulus) or hardness will reduce the line bending of high aspect ratio structures after a mask open step. Finally, an ideal hardmask is easily removed to simplify the fabrication process.
Current hardmasks are insufficient for developing next generation NAND and DRAM devices. As the feature sizes on NAND and DRAM devices decrease, hardmask materials need to exhibit increased etch selectivity and decreased compressive stress properties. However, current attempts at increasing etch selectivity have resulted in an increase in compressive stress, and attempts at decreasing compressive stress have resulted in a decrease in etch selectivity.
Thus, what is needed in the art are methods of forming a hardmask material which exhibits increased etch selectivity while maintaining or reducing the compressive stress of the hardmask material.